i have purchased 18x8 wheels. what tire size would you guys reccomend, and why? what is the widest tire that would fit on the mini? i have a 2003 MCS. stock ride height. most likely planning on staying stock height..
also what places offer the best prices? i live in washington state..

 

You can search for the answer since it has been answered many times.

Look for 205/40-18 as that is the stock MINI 18" runflat size. Limited tires in that size. Other sizes are 215/40-18 which is a little tall. For wider tire try 225/35-18 given your wider than stock 18x8 rim but what is your wheel offset? +42mm? the lower the number the more the wheel sticks out of the wheel well and more risk for rubbing if the tire size is larger than stock.

You have to ask yourself some questions-

Do you want or need runflats?

Do you have cold weather and some snow to drive in with these tires or do you have separate winter wheels and tires?

If you want all weather tires then you need all season Ultra High Performance tires most likely.

What is your budget for tires and how long do you want them to last?

How important are the following in priority-
Handling and performance
Ride comfort
Ride noise
Long treadlife
Cost

Will this be for street use only?

Do you care what the tires look like (aggressive looking tread pattern)?

 

I run 215/40/18 Nitto Neo Gen tires on my MINI. I originally went with the 215/35/18 size, but the side wall was too short for my taste. Plus the ride was a little bumpy.

The reasons I chose 215/40/18; taller side wall and much better ride.

The 215/40/18 tire is actually a tad taller than your stock 17 tire, so it fills up the fender well gap a little.

I really like the Nitto Neo Gen tires. They work well on both wet and dry pavement.

There is recent thread about the Neo Gen tires, you may want to check it out.

The cheapest place that I have found them is at: www.discounttiredirect.com

 

225/35/18 is a great size for the MINI and is perfect on an 8" wheel. Problem is pickings are slim but at least you can get the excellent Goodyear F1 Asymmetric and for a bit less money the Toyo T1R

 

225/35-18 on 18x8 wheel is a more aggressive and performance minded combination vs stock.

True the tire selection isn't the same as with other MINI friendly sizes.

You'll have to do some tire searching to see if any of the choices will fit your needs and budget.

At tirerack.com:
Max Perf Summer tires-
Goodyear Eagle F1 Asymmetric $198 each 240 treadwear (great tire)
Ultra HP Summer tires-
Avon Tech M500 $131 closeout 280 treadwear
BF Goodrich g-Force Sport $133 each 340 treadwear
Yokohama S.Drive $137 each 300 treadwear
Ultra HP All Season tire-
Sumitomo HTR+ $98 each 360 treadwear

And (not at tirerack)
Ultra HP Summer tires:
Nitto NT-555
Toyo T1R